Anonymous Maps allows you to instantiate a map given SQL and CartoCSS. It also allows you to add interaction capabilities using [UTF Grid.](https://github.com/mapbox/utfgrid-spec).
Alternatively, you can get the data for the map (geometry and attributes for each layer) using vector tiles (in which case CartoCSS is not required).
layergroupid | The ID for that map, used to compose the URL for the tiles. The final URL is: `https://{username}.carto.com/api/v1/map/{layergroupid}/{z}/{x}/{y}.png`
Map tiles are used to create the graphic representation of your map in a web browser. Tiles can be requested either as pre-rendered *raster* tiles (images) or as *vector* map data to be rendered by the client (browser).
- **Raster**: If a tile is requested as a raster image format, like PNG, the map will be rendered on the server, using the CartoCSS styles defined in the layers of the map. It is necessary that all the layers of a map define CartoCSS styles in order to obtain raster tiles. Raster tiles are made up of 256x256 pixels; to avoid graphic quality issues tiles should be used unscaled to represent the zoom level (Z) for which they are requested. In order to render tiles, data will be retrieved from the database (in vector format) on the server-side.
- **Vector**: Tiles can also be requested as MVT (Mapbox Vector Tiles). In this case, only the geospatial vector data, without any styling, is returned. These tiles should be processed in the client-side to render the map. In this case layers do not need to define CartoCSS, as any rendering and styling will be performed on the client side. The vector data of a tile represents real-world geometries by defining the vertices of points, lines or polygons in a tile-specific coordinate system.
When you have a layergroup, there are several resources for retrieving layergoup details such as, accessing Mapnik tiles, getting individual layers, accessing defined Attributes, and blending and layer selection.
These raster tiles are PNG images that represent only the Mapnik layers of a map. See [individual layers](#individual-layers) for details about how to retrieve other layers.
[Mapbox Vector Tiles (MVT)](https://www.mapbox.com/vector-tiles/specification/) are map tiles that transfer geographic vector data to the client-side. Browser performance is fast since you can pan and zoom without having to query the server.
CARTO uses Web Graphics Library (WebGL) to process MVT files on the browser. This is useful since WebGL is compatible with most web browsers, include support for multiple client-side mapping engines, and do not require additional information from the server; which makes it more efficient for rendering map tiles. However, you can use any implementation tool for processing MVT files.
The following examples describe how to fetch MVT tiles with a cURL request.
#### MVT and Windshaft
CARTO uses Windshaft as the map tiler library to render multilayer maps with the Maps API. You can use Windshaft to request MVT using the same layer type that is used for requesting raster tiles (Mapnik layer). Simply change the file format `.mvt` in the URL.
**Note**: If no layer type is specified, Mapnik tiles are used by default. To access MVT tiles, specify `https://{username}.cartodb.com/api/v1/map/HASH/{z}/{x}/{y}.mvt` as the `maps_api_template` variable.
**Tip:** If you are using [Named Maps](https://carto.com/docs/carto-engine/maps-api/named-maps/) to instantiate a layer, indicate the MVT file format and layer in the response:
**Note:** By default, [CARTO core functions](https://carto.com/docs/carto-engine/carto-js/core-api/) retrieve URLs for fully rendered tiles. You must replace the default format (.png) with the MVT format (.mvt).
- [Example of MapboxGL Implementation](https://www.mapbox.com/mapbox-gl-js/examples/)
### Individual layers
The MapConfig specification holds the layers definition in a 0-based index. Layers can be requested individually, in different formats, depending on the layer type.
A list of comma separated layer indexes can be used to just render a subset of layers. For example `0,3,4` will filter and blend layers with indexes 0, 3, and 4.
- Ordering is not considered. So right now filtering layers 0,3,4 is the very same thing as filtering 3,4,0. As this may change in the future, **it is recommended** to always select the layers in ascending order so that you will always get consistent behavior.
Anonymous Maps cannot be removed by an API call. They will expire after about five minutes, or sometimes longer. If an Anonymous Map expires and tiles are requested from it, an error will be raised. This could happen if a user leaves a map open and after time, returns to the map and attempts to interact with it in a way that requires new tiles (e.g. zoom). The client will need to go through the steps of creating the map again to fix the problem.
